#show output device, such as VGA-1
xrandr

cvt 1680 1050
# 1680x1050 59.95 Hz (CVT 1.76MA) hsync: 65.29 kHz; pclk: 146.25 MHz
#Modeline "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync

sudo xrandr --newmode "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync
sudo xrandr --addmode VGA-1 "1680x1050_60.00"
sudo xrandr --output VGA-1 --mode "1680x1050_60.00"
